<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    ul{
        width: 100%;
        height: 400px;
        background-color: gray;
        z-index: 2;
        margin: 0 auto;
    }
    li{
        float: left;
        transform: translateX(50%);
    }
    li:nth-child(1){
        width: 500px;
        height: 300px;
        background-color: red;
    }
    li:nth-child(2){
        width: 500px;
        height: 300px;
        background-color: pink;
    }
    li:nth-child(3){
        width: 500px;
        height: 300px;
        background-color: blueviolet;
    }
    li{
        list-style:  none;;
    }

    .next{
        background-color: blue;
        width: 100%;
        height: 300px;
    }
</style>
<body>
    <ul>
        <li></li>
        <li></li>
        <li></li>
    </ul>
    <div class="next">

    </div>
</body>
</html>